Tonometer tips are customarily employed as diagnostic tools by the ophthalmologist and optometrist for measuring ocular pressure to determine the possible existence of glaucoma. In the applanation tonometer an optically transparent tip is releasably mounted in a support housing and disposed on the optical axis of a lens in the housing. The transparent end surface of the tip is placed against the cornea and the ocular pressure is determined by measuring a known force applied over a known area of the corneal contact surface of the tip.
It has long been recognized that at least the corneal contact surface of the tip of the tonometer must be sterilized prior to each measurement or use in order to avoid transmission of disease through tears or lacrimal fluid. The problem of disease transmission has been aggravated in recent years by the recognition of the existence of new diseases and uncertainty as to whether such diseases may be transmitted through tears. For example, much has been written in recent years regarding acquired immune deficiency syndrome (AIDS) caused by infection with the human immunodeficiency virus (HIV). There remains considerable public confusion related to basic facts about the AIDS virus and how it is transmitted. Although HIV has been isolated in the tears of some people with AIDS, tears are not recognized as a mode of transmission. There are no cases of AIDS seroconversion to HIV positive antibody status attributed to tears. Nevertheless, the American Academy of Optometry and the American Academy of Ophthalmology have joined with the Centers for Disease Control in establishing universal infection control protocols. With respect to instruments, the following has been recommended:
"Instruments should be rinsed under running water to remove any organic matter, then disinfected, irrigated with saline and dried. Instruments may be disinfected by heat such as by autoclave for 10 to 30 minutes or by a 10 minute exposure to any of the following fresh (prepared daily) solutions.
1. 0.5% solution (1 to 10 dilution) of common household bleach (sodium hypocholrite)
2. 3% hydrogen peroxide
3. 70% ehthanol
4. 70% isopropyl alcohol.
In recognition of the foregoing, it is to be noted that a soaking period is required for each tip so as to make impractical a temporary or rapid sterilization procedure. For example, one method of sterilization that has been proposed is that disclosed in U.S. Pat. No. 4,735,209 to Foody in which the tonometer has a pivotal housing so that the corneal contact surface can be pivoted into a sterilizing medium without removal from the housing. In U.S. Pat. No. 2,219,417 to Furr, a sterilizer is provided for medical devices which employs a combination of flasks and an electric heating element to boil a sterilizing solution in the flasks and cause the vapors produced to pass through the interior of hypodermic syringes. In U.S. Pat. No. 3,282,090 and 3,511,085 to Posner, et al, means are disclosed for sterilizing tonometers; the '085 patent to Posner, et al., discloses a disposable tonometer tip to facilitate sterilization but does not disclose or suggest a specific means of sterilization. Accordingly, while it is well known to construct applanation tonometers with disposable tips, there is a need for an effective means of sterilization which will facilitate soaking of the tip for any requisite or desired time interval followed by drying and cleaning as a preliminary to each use.